Air-assist discharge of filter press cake

Abstract

A filter press plate shifter assembly (21) provided with a shifter housing (22) having a tunnel-like center part which passes over the filter plates and housing parts positioned adjacent opposite side rails (14). Each side housing part mounts a pneumatic plate shifter (41) for permitting the endmost plate in the closed stack to be individually and sequentially shifted away from the stack into an open position when discharge of filtrate is desired. The shifter housing mounts a bumping device (61) which cooperates with the endmost plate in the stack to effect vertical bumping thereof relative to the support rails to assist in loosening sticky cake which adheres to the plate. The shifter housing also mounts an air-assist discharge mechanism (62) which includes a nozzle-bearing head assembly (80, 80') which moves vertically downwardly between the opposed faces of an open pair of adjacent plates for discharging airstreams downwardly against the plates to assist in removing the sticky cake from the plates. The overall operation of the shifter assembly is fully automated to permit each adjacent pair of plates in the closed stack to be opened, bumped and subjected to an air blast to cause discharge of sticky cake.

Description

FIELD OF THE INVENTION

This invention relates to a filter press and, more particularly, to a plate shifting mechanism for preferably automatically and sequentially shifting individual filter plates into an open position, with the shifting mechanism incorporating vibratory and air blow devices to facilitate removal of filtrate, particularly sticky filtrate, from the open filter plates.

BACKGROUND OF THE INVENTION

Filter presses are well known and extensively utilized for separating solids from slurries. Such presses employ a plurality of filter plates which are held in contacting relationship between fixed and movable head members while the slurry is pumped into and through the press for collecting the solid in the form of filtrate or cake between adjacent filter plates. When the press is full, then the movable head is backed away from the plates into an open position, and in one type of conventional press, the plates are then individually and sequentially moved into an open position adjacent the movable head to permit discharge of the cake which has collected between the adjacent pairs of plates. To permit movement of the plates into an open position, numerous plate shifting mechanisms have been provided for permitting either automatic or manual control over the plate movement and cake discharge.

In the known filter presses, the plate shifter mechanisms often have required various manual controls or manual manipulations associated with the movement of the plate shifter to effect sequential movement of the plates during opening thereof and dumping of the filter cake, although numerous filter press assemblies have incorporated automatic shifting mechanisms to permit such opening and dumping of the plates to be sequentially automated. Most of the automated shifter assemblies, however, have required drive mechanisms such as chains or pressure cylinders positioned adjacent opposite sides of the press, which drive mechanisms themselves are generally elongate throughout substantially the entire length of the press and hence not only increase the overall size and mechanical complexity of the press, but additionally significantly increase the overall cost of the press. These drive mechanisms are also typically disposed in areas where they are subject to contamination by the material being handled. The filter presses employing automated plate shifters have thus possessed structural and functional features which have been less than desirable.

In addition, the known filter presses have also often operated in less than a satisfactory manner when utilized with materials which result in a filtrate or cake having "sticky" properties. That is, when dealing with "sticky" cake, relying solely on gravity to cause discharge of the cake from between the opened filter plates is often insufficient to effect proper discharge since the cake tends to stick to the filter cloths or membranes of the filter plates. It has been conventional practice to manually assist the discharge by having an operator scrape the sticky cake from the filter plates by use of a paddle or the like. Needless to say, this is a very inefficient and time-consuming process. Further, satisfactory cleaning of the filter plates is difficult to achieve using this technique.

In an effort to improve the discharge of sticky cake, filter presses have been developed and sold which have employed a vibrator, one such press being manufactured and sold by Perrin of Canada. In such press, the filter plates are joined together through a control device such as a cable or linkage so that, during opening of the press, all of the plates are substantially simultaneously moved into an open separated condition with the spacing or separation between each adjacent pair of plates being controlled by the connecting linkage. All of the plates, adjacent one side thereof, are supported on an elongate tube which extends longitudinally along the press and is of square or rectangular profile. This tube is then rotated so as to impose a vibration or bouncing movement on the handles provided adjacent one side of the filter plates, whereby all of the plates are vibrated to assist in discharge of the sticky cake. While such arrangement is at least partially effective for permitting discharge of sticky cake, nevertheless this is still of undesirable structure since it requires an additional vibrating drive shaft extending longitudinally substantially throughout the length of the press, and in addition requires a long support frame or support rail arrangement since all of the filter plates are moved into an open and spaced relationship at the same time.

While it is also known to equipped filter presses with liquid washing devices for permitting cleaning of filter plates, nevertheless such devices are typically used only in a very controlled manner and in selected use situations, and typically are not used at the completion of each filter press cycle. More specifically, these washing devices typically spray water on the opened filter plates so as to permit cleaning and flushing of the filter clothes, and hence such will normally be done only infrequently, namely after a selected number of filter press cycles. Further, when such technique is used, it is typically not used to effect discharge of the filter cake since such would significantly increase the amount of liquid in the filter cake, and thus partially destroy the purpose of the filter press operation, namely the removal of liquid.

To improve upon filter presses employing a plate shifter assembly for permitting automatic and sequential shifting of filter plates into open positions during discharge of the press, the Assignee hereof has developed an improved press which is disclosed in copending U.S. Ser. No. 07/904,406, now U.S. Pat. No. 5,370,795. In the press of this latter application, the press is provide with an arch-type shifter housing which extends over and projects downwardly on both sides of the plates so that the downwardly projecting legs of the housing, adjacent lower ends thereof, are rollingly supported on the opposite elongate side rails of the press. Each of the side legs of the housing has a structure which mounts thereon a pneumatic plate shifter mechanism, and in addition one of the housing side legs mounts a pneumatic drive motor which cooperates with a stationary elongate rod which extends parallel to the guide rail to effect driving movement of the housing and shifter mechanism longitudinally along the press. The entire operation, including the movement of the housing in a steplike manner along the press, and the individual sequential shifting of the filter plates and the synchronized movement thereof with the steplike movement of the housing, is pneumatically operated, including a pneumatic logic control for controlling all of the pneumatic drive devices. The improved press of this copending application is believed to represent a desirable improvement over prior conventional structures, although the press of this prior application itself does not satisfactorily resolves the problems associated with discharge of sticky cake. However, many of the mechanisms associated with the shifter of the press of this prior application are incorporated into the present invention, and the disclosure of copending U.S. application Ser. No. 07/904,406, now U.S. Pat. No. 5,370,795, is, in its entirety, incorporated herein by reference.

Accordingly, it is an object of this invention to provide an improved filter press which is particularly desirable for use with materials which create a sticky cake or filtrate, which improved filter press greatly facilitates the discharge of sticky cake and overcomes many of the disadvantages associated with prior filter presses.

More specifically, it is an object of this invention to provide an improved filter press which incorporates devices which subject the filter plates to both a vibrating or bumping action to effect loosening of the sticky cake on the filter plates, and which thereafter subject the open filter plates to an air blow cycle to assist in discharging the sticky cake from the filter plates. The vibrating and air blow operations are preferably sequentially carried out after one of an adjacent pair of filter plates has been moved into an open position to assist in effecting downward discharge of the sticky cake from between the opened pair of filter plates, with the next filter plate thereafter being moved into an open position and the overall process being repeated between the next pair of opened plates.

It is a further object of the invention to provide an improved filter press, as aforesaid, having an improved filter plate shifting assembly which is of the arch-type so as to contain a drive associated with only one side of the filter press, without requiring driving elements extending longitudinally along both sides of the press, which arch-type shifter assembly also mounts thereon devices for effecting both vibrating and air blowing of the filter plates as described above.

It is also an object of this invention to provide an improved filter press which incorporates an air blast system which subjects the open filter plates to an air blow cycle to assist in discharging cake from the filter plates. This air blow system, in a preferred embodiment, incorporates a plurality of discharge nozzles positioned closely adjacent upper edges of the open filter plates to direct discharged high velocity air downwardly against the cake to assist in loosening and discharge of the cake, with the nozzles in the preferred embodiment being vertically displaceable downwardly along the open plates to subject the cake to discharge assisting air either continuously or at selected intervals as the nozzles vertically traverse the open filter plates. In the preferred embodiment, the nozzles discharge air at a velocity which approaches at least supersonic speed, with the nozzles having an air accumulating tank associated therewith to permit the nozzles to emit a high velocity but short duration blast of air, with several such blasts preferably being emitted sequentially at short time intervals as the nozzles traverse vertically of the filter plates.

Another object of the invention is to provide an improved filter press, as aforesaid, having a plate positioning and releasing arrangement associated with the shifter housing to ensure that the filter plate which is shifted into the open position may be disposed a predetermined distance from the closed stack of plates so that the air discharge nozzles are properly positionally related with respect to the open sides of the opposed filter plates, with the open plate then being moved any remaining distance toward the movable head of the filter press after the cake discharge operation has been completed.

Other objects and purposes of the invention will be apparent to persons familiar with presses of this general type upon reading the following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art filter press.

FIG. 2 is a fragmentary side elevational view of the improved filter press according to a first embodiment of this invention and showing the plate shifter assembly positioned for engagement with and shifting of one of the filter plates in the stack when the press is in an open position.

FIG. 3 is an enlarged side elevational view of the plate shifter assembly with a side cover of the shifter housing removed.

FIG. 4 is an end elevational view taken substantially from the leftward end of FIG. 3.

FIG. 5 is an enlarged side elevational view of the lower part of the shifter housing, with an outer side cover removed to show interior details with respect to the plate shifter mechanism.

FIG. 6 is a fragmentary end elevational view, on an enlarged scale, showing a part of the right side of the arrangement shown in FIG. 4.

FIG. 7 is a top view of the arch-type shifter assembly.

FIG. 8 is a partial schematic of the control and driving system.

FIG. 9 is an end elevational view similar to FIG. 4 but illustrating a variation of the support and drive for the air blow device.

FIGS. 10A and 10B are views similar to FIG. 9 but illustrating a further variation of the air blow device.

FIG. 11 is a fragmentary side elevational view of a second and preferred embodiment of the invention, and specifically showing the press in an open position with one of the filter plates being disposed in the open discharge position spaced from the closed stack of plates just prior to initiation of an air-assist discharge cycle.

FIG. 12 is an end elevational view as taken substantially from the leftward end of FIG. 11.

FIG. 13 is an enlarged sectional view of one of the air-assist discharge nozzle assemblies.

FIG. 14 diagrammatically illustrates the air-assist discharge nozzle assemblies as associated with the air-assist discharge head assembly, the air supply therefor, and the control thereof from the master controller of the press.

FIG. 15 is a sectional view of a variation of the control piston arrangement for the nozzle assembly of FIG. 13.

Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words "upwardly", "downwardly", "rightwardly" and "leftwardly" will refer to directions in the drawings to which reference is made. The word "forward" will refer to a direction of movement toward the fixed end of the press, namely rightwardly in FIGS. 1 and 2, and the word "rearward" will refer to the opposite movement direction. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the press and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

DETAILED DESCRIPTION

FIG. 1 illustrates a conventional filter press 11 having a frame 12 which includes a pair of end frames or supports 13 rigidly joined together by a pair of generally parallel and horizontally extending side rails 14 which are sidewardly spaced apart. The press includes a head 15 which is movably supported on the rails 14 for movement toward and away from a further head 16 (FIG. 2) which is fixedly secured adjacent the other end of the frame, with a plurality of conventional filter plates 17 disposed between the heads so as to be held in clamped sealed relationship to one another.

The filter press 11 also includes a plate shifter assembly 21 which includes a generally U-shaped or tunnel-like housing 22 defined by generally hollow housing parts 23 which are disposed adjacent the opposite side rails 14 and rigidly joined together by an arched center part 24 which projects upwardly so as to pass over the filter plates 17 and the movable head 15. This shifter housing 22 is supported for movement horizontally longitudinally along the filter press, and for this purpose is supported on elongate support rods 25 which are fixedly joined by hangers 26 to the respective side rails 14, whereby the support rods 25 are horizontally elongated in parallel relationship to the rails 14 and are spaced sidewardly therefrom by a small distance. Each housing part 23 has a pair of rollers 27 (FIG. 3) provided thereon which are rollingly engaged with the respective rod 25 so that the entire shifter assembly 21 can be moved longitudinally along the press substantially as indicted by arrows 28.

Handles 18 associated with the filter plates 17 are disposed so as to project outwardly from opposite sides of the individual filter plates at an elevation spaced downwardly from the upper edges of the filter plates so as to be slidably supported on the rails 14, whereby the individual filter plates are disposed between and effectively suspended downwardly between the opposed side rails 14. The plates 17 in the filter press are of the type wherein each plate is defined by a generally rectangular outer frame which surrounds a cavity, with a pair of filter cloths or membranes positioned generally so as to extend across the cavity, with the filter cloths being individually carried on the rectangular frame. Such filter plates are of conventional construction, and one example of same is shown in U.S. Pat. No. 4,749,482.

The overall filter press having a general arrangement as described above is conventional. The present invention is directed to improvements in a filter press which incorporates the general structural and functional relationships described above, and such improvements are described hereinafter with reference to FIGS. 2-8 which illustrate a first embodiment of the invention.

To effect driving of the housing 22 longitudinally along the press, the one housing part 23, as illustrated by FIG. 5, has a drive unit 31 mounted thereon. This drive unit 31 includes a grooved drive roller 32 maintained in engagement with the upper side of the respective rod 25. The drive roller 32 is normally of a V-groove profile, and is preferably constructed of a plastic or rubberlike material so as to have high friction and hence a secure rolling driving engagement with the rod 25. The drive roller 32 is driven from a motor 33, this being a direct drive in the illustrated embodiment, although the invention also contemplates provision of a speed reducer such as a gear or chain-type speed reducer between the motor shaft and the driven roller 32. The motor 33 is a bi-directional air-driven rotary drive motor of conventional construction. The motor is mounted interiorly of the tubular housing part 23, and a drive shaft 34 (FIG. 6) for the roller 32 projects outwardly through the inner wall of the tubular housing part 23 so as to position the roller 32 in driving engagement with the adjacent rod 25. The roller 32 may, if desired, be maintained in spring-urged driving engagement with the rod, and one example of such arrangement is illustrated in aforementioned copending Ser. No. 07/904,406, now U.S. Pat. No. 5,370,795. The drive unit 31 is provided on only one of the housing parts 23, the other side of the shifter housing 22 being free of such drive unit.

A holding or braking device 35 (FIG. 5) is provided on one, and preferably both, housing parts 23 for braking engagement with the rods 25 when the drive unit 31 is de-energized. Each braking unit 35 includes a generally C-shaped yoke or carrier 36 disposed directly adjacent the sidewall-of housing part 23 and mounted thereon through vertical slots (not shown) so that the carrier 36 can undergo limited vertical displacement relative to the housing part 23. The C-shaped configuration of the carrier 36 is oriented so that it projects toward and partially surrounds the adjacent support rod 25, and a small air-actuated pressure cylinder 37 is mounted adjacent the upper end of the carrier 36 and has the piston rod thereof joined to an upper brake pad 38. A lower brake pad 39 is secured to the carrier 36 adjacent the lower end thereof. The brake pads 38 and 39 are respectively disposed directly over and under the rod 25 and, when the cylinder 37 is pressurized, the upper pad 38 is pushed downwardly to react against the rod 25, thereby causing the carrier 36 to shift upwardly so that the lower pad 39 also reacts against the rod 25, thereby creating a braking or holding engagement with the rod 25 between the opposed pads 38 and 39. These pads are preferably constructed of hard plastic and/or rubberlike materials. A spring (not shown) is provided interiorly of the air cylinder 37 for returning it to its retracted position, and a further spring (not shown) coacts with the carrier 36 for normally urging it towards its lower position to disengage the lower pad 39 from the rod 25.

Each housing part 23 of the shifter assembly 21 also mounts thereon a plate shifter 41 (FIG. 5) which includes a fluid pressure cylinder 42 (herein referred to as the shift cylinder), preferably a double-acting air cylinder, having a conventional cylindrical housing 43 from one end of which a piston rod 44 slidably projects. The other end of cylinder housing 43 is secured to a bracket 45 through a pivot or trunnion 46, the latter projecting horizontally in perpendicular relationship to the longitudinal direction of the press so that the entire shift cylinder 42 is vertically swingable about this pivot.

A first shifter member or blade 47 is fixedly secured to the free end of the piston rod 44, and a second shifter member or blade 48 is fixedly secured to the end of the cylinder housing 43 through which the piston rod projects. The shifter blades 47-48 are both platelike members which extend transversely of the piston rod in generally parallel relationship so as to substantially directly overlap when the piston rod is in the retracted position illustrated by FIG. 5.

The plate shifter 41 also includes a guide assembly defined by an elongate guide tube 49 fixed to and extending parallel along the cylinder housing 43, and an elongate guide rod 51 slidably supported within the guide tube 49 with one end of rod 51 projecting outwardly though the blade 48 for securement to the blade 47. Whenever the piston rod 44 is extended, then guide rod 51 is also extended and prevents rotation of the blade 47.

The plate shifters 41 as disposed on opposite sides of the press are normally maintained in lowered inactive positions, substantially as illustrated by dotted lines in FIG. 5. To move the plate shifter into a raised positions for engagement with the filter press plates, which raised position is indicated by solid lines in FIG. 5, there is provided a lifting mechanism 52 mounted in each housing part 23 for cooperation with the respective plate shifter 41. The lifting mechanism 52 includes a lifting cylinder 53 which, like the shift cylinder 42, is a double-acting pneumatic cylinder having a cylindrical housing 54 fixed relative to the housing part 23 and a piston rod 55 slidably extendible from the upper end thereof. This piston rod 55, at the upper free end thereof, has a suitable cap which abuts against the underside of a plate 56 secured to the underside of the guide tube 49. Lifting cylinder 53 is normally maintained in a lowered or contracted position illustrated by dotted lines in FIG. 5 to normally maintain the plate shifter 41 in the lowered inactive position. When lift cylinder 53 is energized to extend the piston rod 55 upwardly, which upward extension is limited by an internal stop, then the plate shifter 41 is moved into the operative or shifting position illustrated by FIGS. 3 and 5.

To position the plate shifter 41 in adjacent and proper positional relationship relative to the leading or endmost filter plate 17 in the closed stack (i.e., the stack of plates which extends outwardly away from the stationary head 16), the plate shifter assembly 21 on one side of the housing 22 in the vicinity of but spaced upwardly from the blades 47-48, is provided with a plate sensor 57 (FIG. 6). This plate sensor 57, in the illustrated embodiment, comprises a conventional limit switch which is opened and closed by an elongate switching or sensing lever 58 which is normally maintained (as by spring-urged) in a position wherein it projects inwardly within a generally vertical plane so as to be positioned for contact with the handles 18 provided on one side of the filter plates 17. When sensing lever 58 contacts one of the plate handles 18, the lever 58 is horizontally swung or displaced and causes actuation (i.e., opening) of the sensor 57 to effect stoppage of the drive motor 33 of the shifter assembly 21.

To assist in removal of sticky sludge from the filter plates during discharge, the filter press of this invention as shown in FIGS. 3 and 4 also incorporates a filter plate vibrating or bumping mechanism 61, and an air blow discharge assist mechanism 62, both of which are mounted on the housing 22 of the shifter assembly so as to be movable therewith as the shifter assembly effects sequential shifting of the filter plates into an open discharge position.

Considering first the vibrating or bumping device 61, a pair of such devices 61 are provided, being disposed on the opposite side legs of the arch-shaped housing 22 so as to be positioned adjacent opposite sides of the press. Each device 61 includes a fluid pressure cylinder 63, namely a double-acting air cylinder, having a housing or cylinder 64 (FIG. 6) fixed to the shifter housing 22 and oriented so that the piston rod of the cylinder 63 projects vertically upwardly through the upper end for vertical extension. The piston rod of each bump cylinder 63 has the upper outer end thereof fixed to a generally L-shaped bump or impact member 65 (FIG. 6) which includes a leg part 66 which projects downwardly and is vertically slidably guided along one side of the cylinder housing 64. This leg part 66 in turn has a bumping tab or projection 67 projecting horizontally therefrom inwardly toward the adjacent upper corner of a filter plate 17. Each filter plate 17 is also provided with a lifting bracket 68 fixedly secured to each upper corner thereof. The lifting bracket includes a cantilevered lifting tab 69 which projects horizontally outwardly in a sideward direction away from the upper corner of the filter plate, whereby the lifting tab 69 projects so as to be disposed above and overlap the bumping tab 67, the latter tabs being normally vertically spaced a small distance apart when the plates 17 are supported on the press rails 14 by the handles 18 and the bump cylinders 63 are in their retracted (i.e., lowered) positions.

The bump cylinders 63 are mounted on the shifter housing 22 at a position whereby the bump tabs 67 are sidewardly aligned directly under the lifting tabs 69 associated with the front or endmost filter plate associated with the closed stack, such as the filter plate designated 173 in FIG. 3.

The bump cylinders 63 are normally maintained in the lower retracted position and are activated only during the discharge cycle of the press. When the press is in the discharge cycle, pressurized air is rapidly and alternately supplied first into the lower ends and then into the upper ends of the bump cylinders 63, which cycle is preferably repeated two or three times in rapid succession, to cause at least two rapid cycles of lifting and lowering of the endmost filter plate 17.sub.2 relative to the adjacent plate 17.sub.3. This lifting is illustrated by the dotted line position of the filter plate in FIG. 6. The lifting is normally no more than about two inches, and occurs with sufficient rapidity so as to effectively result in free fall of the lifted filter plate until the handles 18 of the lifted plate contact the press rails 14 and impose a bump or impact on the plate which is effective in at least partially loosening the sticky filtrate or cake which is adhered to the plate. The vertical displacement of the plate 17.sub.2 relative to adjacent plate 17.sub.3 also assists in effecting at least partial loosening of the sticky filtrate relative to the filter cloths of the adjacent filter plates.

Considering now the air blow discharge assist mechanism 62, and referring specifically to FIGS. 3 and 4, this mechanism is mounted on a generally arch-shaped or tunnel-like shroud 71 which is fixed to one end of the shifter housing 22 and projects longitudinally along the press in a direction toward the movable head 15 so as to effectively enclose at least opposite sides of the gap or discharge region defined between the opposed pair of opened plates, such as represented by the plates 17.sub.1 and 17.sub.2 in FIG. 3. This shroud 71 effectively comprises and constitutes an extension of the shifter housing 22 in that it includes a top wall 72 which extends sidewardly across the press in upwardly spaced relationship from the filter plates, and a pair of sidewall portions 73 which project downwardly from the top wall 72 adjacent opposite sides of the press in sideward straddling relationship to the filter plates.

The discharge assist mechanism 62 includes a pressure cylinder 75, preferably a double-acting pneumatic cylinder. This pressure cylinder 75, herein referred to as the blow or discharge cylinder, includes a cylinder housing 76 which has a lower end thereof secured to a mounting plate 77, the latter being fixed to support arms 78 which are fixed to and project outwardly from the top wall of the shifter housing 22. The discharge cylinder 75 is vertically oriented and has the piston rod 79 thereof disposed so as to slidably project vertically downwardly through the lower end thereof, which piston rod 79 in turn is coupled to an air discharge head assembly 80 which includes a manifold block or nozzle head member 81 which is horizontally elongated transversely (i.e., perpendicularly) across the press. This manifold block 81 has a transversely extending length which is of a magnitude similar to the width of the filter plates.

The manifold block 81 also has a pair of vertically upwardly projecting guide rods 82 fixed thereto in straddling relationship to the piston rod 79. These guide rods 82 are vertically slidably supported in bearing blocks 83 secured to the mounting plate 77, and the upper free ends of the guide rods 82 are joined together by a connecting plate 84.

The transversely extending manifold 81 has rows of air discharge nozzles 85 projecting outwardly from opposite sides thereof so that the nozzles 85 of one row project generally toward the exposed face of the open filter plate (such as plate 17.sub.1), and the nozzles 85 of the other row project generally toward the exposed face on the endmost filter plate of the closed stack (such as plate 17.sub.2). The opposed rows of nozzles 85 project horizontally outwardly in opposite directions from the manifold 81 through a sufficient extent longitudinally of the filter press so that the discharge ends of the nozzles 85 are positioned closely adjacent the exposed faces of the opposed open filter plates 17.sub.1 and 17.sub.2 when the manifold 81 is moved vertically downwardly into the gap or region between the opposed opened filter plates, as explained below.

The manifold 81 has air passages (not shown) disposed interiorly thereof for communication with the nozzles 85, which nozzles are disposed within a generally transverse horizontally extending row in substantially uniformly spaced relationship so that a plurality of nozzles are disposed closely enough together to effect discharge of several adjacent airstreams against the exposed face of the filter plate, with the airstreams traversing downwardly during operation of the discharge assist mechanism 62. The manifold 81 is supplied with pressurized air through an air supply conduit 86, the lower end of the which is fixed to the manifold 81. The upper end of conduit 86 is fixed to the connecting plate 84 so that the conduit 86 is vertically displaceable in unison with the guide rods 82. A flexible air supply hose or conduit 87 has one end thereof coupled to the upper end of supply conduit 86, and the other end of hose 87 couples to an air supply conduit 88 which is fixed to the shifter housing 22.

The shifter housing 22 mounts thereon a control housing, indicated diagrammatically at 89 in FIG. 3, the latter being surrounded by a suitable cover 91. The control housing contains therein the pneumatic and electrical controls for operation of the shifter, with the pneumatic controls (including valves and other conventional pneumatic control devices) being supplied with pressurized air in a conventional manner from an exterior pressure source.

As illustrated by FIGS. 3 and 4, the discharge cylinder 75 normally maintains the air discharge head assembly 80 (namely the manifold 81 and nozzles 85) in an upper inactive position wherein this air discharge head assembly 80 is spaced upwardly from the upper edges of the filter plates 17. The air discharge head assembly 80 is maintained in this upper position by closing off the discharge cylinder 75 so that air is locked in the cylinder to maintain the piston rod in the upwardly contracted position. During air-assisted discharge of filtrate from the filter plates, however, then cylinder 75 is energized to extend the head assembly 80 downwardly into the gap between the opposed and spaced pair of opened plates and, during this downward traverse, air is constantly discharged through the nozzles 85 so that a plurality of airstreams are directed against and moved vertically downwardly across the exposed faces of the filter plates to assist in discharging the sticky filtrate. The air discharge head assembly 80 moves downwardly a sufficient stroke so as to effectively traverse the complete face of the filter plates, and then the discharge cylinder 75 is reversed and moved upwardly to its upper position, at which time the air supply to the manifold 81 is terminated and the cylinder 75 is pneumatically held in its raised position.

Referencing now FIG. 8, there is diagrammatically illustrated pneumatic and electrical control relationships associated with the shifter so as to effect automatic sequencing of the shifter assembly 21 to sequentially effect discharge of cake from between adjacent pairs of filter plates. More specifically, pressurized air is supplied from an external source 92, such as a compressor, through a main control valve V.sub.1, the latter controlling the supply pressurized air to the press. One valve V.sub.2 is provided for controlling flow of air to the two supply ports of the motor 33 so as to not only control energization of the motor 33, but also the direction of rotation thereof. A valve V.sub.3 controls flow of air to the double-acting bump cylinders 63, a valve V.sub.4 controls flow of air to the double-acting lift cylinders 53, a valve V.sub.5 controls flow of air to the brake cylinders 37, a valve V.sub.6 controls flow of air to the double-acting shift cylinders 42, a valve V.sub.7 controls flow of air to the double-acting discharge cylinder 75, and a valve V.sub.8 controls flow of air to the manifold 81. These valves are of conventional configuration, and are typically electrically-actuated by appropriate signals received from a master press controller 93, the latter preferably comprising a microprocessor. The controller 93 provides appropriate control signals designated i through p to the valves V.sub.1 through V.sub.8 respectively so as to control the operation thereof.

The controller 93 in turn receives appropriate signals designated a through h from position sensing switches associated with the various pneumatic drivers, specifically the air cylinders 42, 53, 63 and 75.

More specifically, each bump cylinder 63 has position sensors such as magnetically-actuated reed switches S.sub.1 and S.sub.2 associated therewith for sensing the respective extended and contracted positions, with the two switches S.sub.1 being connected in series, and the two switches S.sub.2 connected in series, whereby each cooperating pair emits a control signal a or b to the controller 93 only when both cylinders 63 are in the respective extended or contracted positions.

Similarly, the lifting cylinders have switches S.sub.3 and S.sub.4 (such as magnetic reed switches) which designate the respective extended and contracted positions, with switches S.sub.3 being connected in series and emitting a control signal c to controller 93 only when both lift cylinders are extended, and similarly switches S.sub.4 being connected in series to emit a control signal d to controller 93 only when both lift cylinders are in the lowered or contracted positions.

The shift cylinders 42 have position sensors formed as switches S.sub.5 and S.sub.6 (such as Hall effect sensors) which respectively define the extended and contracted positions of the shift cylinders 42. The two switches S.sub.5 are connected in series, as are the two switches S.sub.6, and these respectively emit control signals e and f to the controller 93.

Lastly, pressure cylinder 75 has position sensors S.sub.7 and S.sub.8, again normally formed as magnetic-actuated reed switches, for respectively indicating the upper retracted and lower extended positions. These switches in turn emit control signals g and h to the controller 93.

The controller 93 emits control signals to the various valves, such as V.sub.1 through V.sub.8, in response to control signals a through h as received from the various air cylinders so as to ensure proper automatic sequencing of the various devices and mechanisms.

The controller 93 also receives a signal from the position sensor 57 when the latter contacts and is activated by the handle 18 on the endmost filter plate 17 of the stack so as to effect stoppage of the drive motor 33.

The press 11 is also normally provided with appropriate position sensors such as limit switches LS1 and LS2 disposed adjacent opposite ends of the support rod 25, which limit switches sense the presence of the shifter housing 22 when it reaches the end positions so as to control the shifter assembly 21. For example, limit switch LS1 is normally disposed adjacent the leftward end of the press in FIG. 1 so as to function as a "home" sensor to normally maintain the shifter assembly 21 in a stationary "home" position adjacent this end of the press, such as during the filling cycle of the press. The other limit switch LS2 is disposed adjacent the other end of the press, namely the rightward end in FIG. 1, to sense when the shifter assembly 21 has moved along and effected sequential opening of all of the plates, whereupon the switch LS2 effects reversal in the rotation driving of motor 33 so as to return the entire shifter assembly 21 to its home position.

There is preferably provided an additional switch S.sub.t which is effectively a start switch which can be manually activated if desired so as to permit initiation of the press opening and discharge cycle.

The operation of the filter press of the present invention, as explained above, will now be briefly described to ensure a complete understanding thereof.

The shifter assembly 21 will normally be maintained at the leftwardmost end (FIGS. 1 and 2) of the press, this being the normal home position. When emptying of the press is desired, a signal will be transmitted to the press controller 93, either manually from the start switch S.sub.t or from a portion of an automatic controller, such as a microprocessor, which controls the overall press operation. Controller 93 then supplies a signal to valve V.sub.2 to effect opening thereof so that pressurized air will be supplied to motor 33 to effect "forward" rotation thereof. This drives roller 32 and causes the entire shifter assembly 21 to move forwardly (rightwardly in FIGS. 1 and 2) along the rods 25 until the shifter housing 22 passes over the head 15 (which has already been moved into an open position wherein it is spaced a predetermined distance from the endmost movable filter plate 17.sub.1) and over the endmost ones of the closed stacked filter plates 17. In this regard, the endmost filter plate 17.sub.1 is normally fixed to and moves with the movable head 15. When the shifter assembly 21 approaches the endmost movable plate 17.sub.2, the plate sensing lever 58 contacts the handle 18 of the endmost plate and is angularly deflected through a small angle. This activates the plate sensor 57 so as to transmit a signal to the controller 93 which then stops the motor 33. A signal m is emitted to the valve V.sub.5 which energizes the brake cylinder 37 so as to apply the brake devices 35. After a predetermined but short time delay as controlled by the controller, the controller 93 then emits a signal k to valve V.sub.3 which permits cyclic up-and-down actuation of the bump cylinders 63, preferably for at least two up-and-down cycles. That is, the controller 93 emits appropriate signals to valve V.sub.3 so as to cause rapid extension followed by rapid contraction of the cylinders 63, this being performed preferably at least twice in rapid sequence. This causes the bump tabs 67 to engage the filter plate lifting tabs 69 and effect rapid upward lifting of solely the endmost filter plate 17.sub.2 a small distance, followed by downward dropping of the plate 17.sub.2 against the rails 14 due to the rapid retraction of the cylinders 63. This cycle is preferably repeated at least two times in sequence. During this cyclic lifting and lowering of the filter plate 17.sub.2, the downwardly free fall of the plate and its impact on the rails 14, which is referred to herein as vertical bumping of the filter plate, is effective for causing at least partial dislodgement or loosening of the sticky cake which is adhered to not only the exposed face of the plate 17.sub.2, but also to the face of plate 17.sub.2 which faces the adjacent plate 17.sub.3. This bumping of the plate has been observed to effect sufficient loosening to create a slight gap between the sticky cake and the filter cloth, particularly adjacent the upper perimeter of the cloth and cake. After the controller 93 completes the cyclic activation of the bump cylinders 63, and return of the bump cylinders to the lower retracted positions is sensed by the position sensors S.sub.2 so as to emit a control signal b to the controller 93, then the controller 93 emits an appropriate control signal o so as to activate the air discharge assist device 62.

More specifically, valve V.sub.7 is activated to supply air to the upper end of blow cylinder 75, and simultaneously valve V.sub.8 is activated to supply air to the manifold 81. The head assembly 80 is then moved downwardly into the gap between the opposed open plates 17.sub.1 and 17.sub.2. The nozzles 85 are disposed closely adjacent the opposed faces of the open filter plates, and in fact the nozzles are preferably oriented so they eject a plurality of sidewardly adjacent airstreams which are directed outwardly but downwardly (such as at an angle of about 45.degree.) toward the opposed exposed face of the filter plate. These airstreams are able to enter into the narrow gaps created between the filter cake and the underlying filter cloth and effectively assist in peeling the sticky filter cake away from the filter cloth. As the head assembly 80 is lowered vertically downwardly between the opposed filter plates throughout substantially the vertical extent thereof, these airstreams are directed outwardly and downwardly generally into the interface region between the sticky cake and the filter cloth so as to effectively progressively peel the filter cake away from the cloth as the nozzles move vertically downwardly. Of course, the weight of the cake itself may additionally assist in peeling away the sticky cake as a greater portion of the cake is peeled outwardly away from the underlying filter cloth.

After the head assembly 80 reaches it lowermost position, then position sensor S.sub.8 emits a signal h to controller 93 which emits a control signal to valve V.sub.7 so as to reverse flow of pressurized air to blow cylinder 75, thereby causing the cylinder 75 and the head assembly 80 to be retracted upwardly into their uppermost position as illustrated by solid lines in FIG. 3. During this upward retraction, however, air is continually supplied to manifold 81 so as to effect further blowing of airstreams against the opposed filter plates to effect some additional supplemental cleaning thereof, if necessary. Upon reaching the uppermost position, position sensor S.sub.7 emits a signal g to the controller which then deactivates the appropriate valves to hence deactivate supply of pressure fluid to the cylinder 75 and manifold 81, whereby the cylinder is pneumatically locked in the raised position.

Upon receipt of signal g at the controller, the controller then emits a signal l so that valve V.sub.4 is controlled to supply pressurized air to the lower ends of lifting cylinders 53 to effect extension thereof. When the cylinders 53 effect upward lifting of the plate shifter 41 into its upper position, as sensed by the position sensors S.sub.3, then a signal c is transmitted to the controller 93 which in turn then emits a signal to control the valve V.sub.6 of the shift cylinders 42. At this time, the shift blades 47-48 have the upper ends thereof inserted into the narrow gap between the handles 18 of the endmost pair of closed plates 17.sub.2 and 17.sub.3. Energization of cylinders 42 results in the movable shifting blades 47 being projected outwardly (leftwardly in FIGS. 3 and 5) toward the movable head 15, whereby the movable blades 47 contact the side handles 18 on the endmost plate 17.sub.2 so as to slide this filter plate along the rails 14 toward an open position adjacent the head 15. When the shift cylinders 42 reach their fully extended positions, the shifted plate 17.sub.2 is disposed in an open position wherein it abuts the plates stacked against the movable head 15, and is spaced a predetermined longitudinal distance from the endmost plate 17.sub.3 of the closed stack. During this extension of the shift cylinders 42, the stationary blade 48 will, if necessary, due to slight shifting of the housing 22, react against the adjacent plate 17.sub.3 to prevent any significant movement of the shifter housing 22. When the controller 93 receives the signal e indicating full extensions of the shifter cylinders 42, then the controller 93 signals valve V.sub.6 so that the shift cylinders 42 are retracted, followed by lowering of the lift cylinders 53. The lowered lift cylinders 53 emit a control signal d to controller 93 which signals completion of the discharge cycle for one pair of plates.

The controller 93 will initiate a new cycle by transmitting appropriate signals which release the brake devices 35 and which again energize the motor 33 to effect forward rotation until the switching sensor 58 contacts the handle of the next adjacent plate 17.sub.3, whereupon the complete cycle is again automatically carried out in the same manner as described above.

The shifting and discharge cycles continue until the last movable filter plate 17 is shifted and discharged of filtrate, at which time the shifter housing is again moved forwardly until contacting the limit switch LS2, at which time the controller signals the motor 33 so that the rotational direction is reversed. This causes the entire shifter assembly 21 to then be moved rearwardly (leftwardly in FIGS. 1 and 2) along the rods 25 until the shifter assembly reaches its home position as sensed by the switch LS1 which then deactivates the shifter assembly until such time as a new start signal is received.

It will be understood that the filtrate or cake as discharged from the plates is deposited into a suitable collecting bin or the like as disposed below the press.

The pneumatic and electrical controls illustrated in FIG. 8 are only partially and schematically shown since it will be understood that the specific valves, switches and other related controlling devices are themselves conventional, and can assume many different configurations so as to still provide the desired control functions, as will be readily apparent to those of ordinary skill in such technology.

While the blow discharge assist mechanism 62 as described above, wherein the vertically-extending blow cylinder 75 is provided for controlling the vertical cycling movement of the discharge head assembly 80, is desirable from a structural and operational simplicity standpoint, it will be appreciated that such arrangement also does require significant overall height in order to have all of the moving components vertically aligned. Thus, other drive mechanisms can be provided for controlling vertical cyclic movement of the head assembly 80. Examples of additional drives for the blow discharge assist mechanism are illustrated in FIGS. 9 and 10.

More specifically, in FIG. 9 the head assembly 80 is driven by and connected to a pair of elongate chains 101 which abut back-to-back where they connect centrally to the manifold 81. The chains 101 project upwardly and individually pass over driven counter-rotating drive sprockets 102 which are rotatably supported on the shifter housing at an elevation above the filter plates. These drive sprockets cause the chains 101 to retract horizontally, either sidewardly of the press or longitudinally thereof, into appropriate guide tracks indicated diagrammatically at 103. The chains 101 are of the type which are capable of effecting driving both by pushing and pulling. That is, the links of the chain have direct solid abutments therebetween which permit pushing forces to be transmitted along the chain, and which permit the chain links to hinge only in a single direction away from the straight line condition, whereby when the chains are disposed in back-to-back relationship, hinging of the chains is effectively prevented and the chains can thus provide a rather rigid link for controlling the up-and-down movement of the manifold head. The construction of such chain is conventional. The sprockets can be driven through suitable gears by a single reversible drive motor if desired, which drive motor can be controlled by appropriate signals received from the controller 93.

The arrangement of FIG. 9 is desirable for use in those situations where minimal height is available, since such transversely (i.e., horizontally) projecting drive arrangement enable the overall height of the press to be reduced.

FIGS. 10A and 10B illustrated another variation of a drive device for the air discharge assist mechanism 62, which modified drive device is also of minimal height. In this embodiment, the mechanism 62 includes a double-acting pneumatic cylinder 104 which is oriented horizontally in the sideward direction of the press so that the piston rod is slidable horizontally transversely of the press along the centerline 105. The piston rod of the cylinder 104 projects outwardly from one end and has a bracket 106 secured thereto, the latter being coupled by a pivot 107 to the upper free end of one upper link 108 of a scissor mechanism 109, specifically a lazy tong mechanism. This mechanism 109 includes a further upper link 110 pivotally joined to link 108 by central pivot 111, and the upper end of the link 110 is joined by a pivot 112 to a stationary bracket 113 secured to the shifter housing. Links 108, 110 in turn have the lower ends thereof pivotally joined to respective upper ends of links 114 and 115, the latter being centrally joined by a pivot 116, and having their lower ends pivotally joined at 117 and 118 to a support bar 119 which mounts and extends lengthwise along the manifold 81 of the head assembly 80. The connection of pivot 118 to the support 119 involves a slide member 121 which is movable lengthwise along the support bar 119 when the mechanism 109 is moved from the raised contracted position of FIG. 10A to the lowered extended position of FIG. 10B.

Reference will now be made to FIGS. 11-14 which illustrate a second embodiment of a filter press according to the present invention, which embodiment incorporates therein a preferred variation of the air blow discharge assist mechanism 62'. This discharge assist mechanism 62' is used in place of the discharge assist mechanism 62 described above. Corresponding parts of the discharge assist mechanism 62' and of the press are designated by the same reference numeral utilized above except for the addition of a prime (') thereto.

In the air blow discharge assist mechanism 62', the head assembly 80' is vertically moved by a scissor mechanism 109' which effects downward vertical displacement of the head between the opened plates, followed by upward displacement into an upper inactive position, with this scissor mechanism being utilized in this embodiment to permit minimization in overall height. The head assembly 80' includes a horizontally elongate head member 131 which extends traversely of the press and is fixedly secured to a lower support rail 119' of the scissor mechanism by suitable brackets 132. Two rows of nozzle assemblies 133 are provided on the head assembly, with one row being on each side thereof and oriented so as to cooperate with an adjacent one of the two opposed filter plates disposed in an opened position and from which the filtrate or cake is to be removed. Each of these rows has a plurality of substantially identical nozzle assemblies 133 disposed in uniformly spaced relationship therealong, with five such nozzle assemblies being provided in each row in the illustrated embodiment.

The nozzle assembly 133 is formed as an air blaster for emitting a high velocity but short duration air jet, such as a pulse of high velocity air, and preferably employs a converging-diverging nozzle of the type commonly known as a Laval nozzle, so that the discharged air is at a very high velocity. Such Laval nozzles are generally designed to achieve velocities which approach or exceed sonic velocity.

Referencing FIG. 13, there is illustrated a construction of the nozzle assembly 133 so as to provide this desired blast or pulse function. This nozzle assembly 133 includes a closed storage tank 134 defining therein a closed chamber 135 of limited capacity, which chamber 135 in a typical example will have a volume which is significantly less than one cubic foot, and in fact the volume of this chamber will more typically be in the neighborhood of about 0.1 to about 0.5 cubic foot for supplying one nozzle. A pipe or tube 136 is positioned closely adjacent (and in the illustrated embodiment penetrates) the tank 134 and includes an air supply part 137 at one end which joins to a control part 138 adjacent the other end, this latter part 138 terminating in a flange 139 which is fixedly secured to the tank, as by fasteners 141. An air supply passage 142 extends through the part 137 and opens into one end of an enlarged cylindrical chamber 143 as formed in the control part 138. A plurality of ports or openings 144 extend radially through the part 137 for providing controlled communication from the passage 142 into the chamber 135, and for this purpose suitable check valves and more specifically ball valves 145 are sealingly seatable against the outer ends of the ports 144 to selectively close off the ports and function as one-way check valves to prevent reverse flow from the chamber 135 back into the passage 142. A suitable low-force resilient ring 146 or similar spring device is provided to maintain the valve balls seated against the seats except when pressurized air is flowing through the ports into the chamber 135.

An annular nozzle member 147 is fixedly secured within the outer end of the cylindrical chamber 143 and defines a converging-diverging nozzle opening 148 therein, this being commonly referred to as a Laval nozzle. A Laval-type nozzle is a nozzle with a throat and expanding exit so that if a sufficient ratio of internal pressure to external pressure exists the gases may expand beyond the throat, thus yielding supersonic speeds. In this invention, the nozzle opening 148 includes a converging upstream portion defined by the tapered annular converging wall 151, with this converging nozzle portion being joined to a central nozzle portion of minimal diameter as defined by the surrounding central cylindrical wall 152. This central nozzle portion in turn communicates with a diverging nozzle portion defined by the surrounding tapered diverging annular wall 153. This diverging portion 153 at its maximum diameter communicates with a discharge nozzle passage 154 which, at its junction with the tapered wall 153, is of generally similar diameter. This discharge nozzle passage 154 is aligned with the nozzle and is axially elongated, and is defined by an axially elongate nozzle member extension 155 which is fixed to and projects axially outwardly from the nozzle member. This nozzle member extension terminates in a discharge opening 160 at the free end thereof.

The nozzle assembly further includes a control piston or valve 157 which is of generally cylindrical cross section and is disposed within the cylindrical chamber 143 so as to be axially slidable therein, while at the same time the slidable fit of the piston 157 within the chamber 143 is such as to prevent any significant leakage past the walls thereof. This control piston 157 defines thereon a rear face 158 which is exposed to the pressure fluid (i.e. air) supplied through the air passage 142. The control piston 157, at the other end thereof, is provided with a seating face 159 which, in the illustrated embodiment, is of a truncated conical configuration which converges as it projects toward the free end of the control piston, with the convergence being inclined similar to that of the nozzle member wall 151 so that this seating face 159 can move into substantially sealing engagement with the nozzle face 151.

The tubular part 138 is also provided with at least one and, in the illustrated embodiment, eight ports or orifices 156 which project radially through the wall of the part 138 to provide for communication between the storage chamber 135 and the control chamber 143. These ports 156 communicate with the control chamber just upstream of the nozzle member 147 and, as illustrated by FIG. 3, the front or lower end of the control piston 157 has an end face (as defined by a part of the seating face 159) which partially overlaps (or in fact may be disposed rearwardly of) the orifices 156 so that some of the pressure fluid in storage chamber 135 can pass through orifices 156 and act against this small-area rear face to exert a force on the control piston 157 tending to move it (upwardly in FIG. 13) in an opening direction.

To supply pressurized air to the plurality of nozzle assemblies 133 associated with each of the two rows on the head assembly 80', air is typically supplied from a pressure source S (FIG. 14) which may be a separate compressor unit but which is typically the centralized air supply as provided in a plant and is piped throughout the plant to various equipment. Such central air supplies typically are maintained at a pressure in the neighborhood of about 100 psi. The pressurized air from this supply S can be suitably supplied to the filter press through a main control valve 161 which can be utilized to turn on or off the air supply to the nozzle assemblies associated with the press. The pressurized air supplied through the control valve 161 is supplied to a main supply line 162 which in turn supplies a plurality of branch lines 163, each having a control valve 164 associated therewith, the latter being a typical three-way valve which permits the pressurized supply air to be supplied either to a load (i.e., the nozzle assembly) or to the atmospheric (i.e., a discharge tank). Each branch line 163 containing its own control valve 164 in turn joins to a pair of individual supply lines 165, the latter being connected to an opposed pair of nozzle assemblies 133. In this illustrated embodiment, each opposed pair of nozzles (that is, one of the nozzles in one row, and the directly adjacent nozzle in the other row) are controlled by a respective valve 164, but it will be appreciated that several pairs of nozzles (and in fact all five pairs if desired) could be controlled by a single valve 164 if desired. These individual supply lines 165 in turn communicate with the respective air passages 142 associated with the nozzle assemblies 133. Each control valve 164 can also be shifted to allow the passage 142 to communicate with a low-pressure drain or exhaust line 166.

To use the nozzle assembly 133, pressurized air supplied to passage 142 causes the control piston 157 to move into a closed position, and causes pressurized air to flow into and build up within the closed storage chamber 135, thereby creating an isolated but confined volume (i.e. a charge) of pressurized air. When the pressure in passage 142 is momentarily decreased to substantially atmospheric, such as by opening the passage 142 to the exhaust or drain 166 by the control valve 164, then the pressurized fluid acting through ports 156 on the lower end face of control piston 157 causes this piston 157 to be rapidly moved upwardly into an open position, thereby opening the nozzle member 148, and then permitting the confined quantity of highly pressurized air within the storage chamber 135 to rapidly discharge through orifices 156 with this air being effectively blasted through the nozzle member 148 and then discharged through the opening 160 at a velocity which approaches or exceeds sonic velocity, with this blast of high velocity air occurring only for a very short duration which is significantly less than one second and, in fact is generally no more than about 100 milliseconds.

The control valve 164 is also normally opened for a short duration of time, such as about 100 milliseconds, and then can be immediately reclosed. At this time the pressurized air within chamber 135 has already been discharged, and hence pressurized air is again supplied from the supply S into passage 142 to cause the control piston 157 to close, and the chamber 135 to again be filled up with a further charge of high pressure air.

Each nozzle assembly 133 in the illustrated embodiment is mounted to the head member 131 by a suitable bracket assembly which permits the nozzle assembly to be both sidewardly and longitudinally adjustably tilted relative to the adjacent filter plate. This mounting arrangement includes a bracket 167 which projects outwardly from the head member and employs a horizontal swivel axis 168 which extends in the longitudinal direction of the press. This bracket 167 in turn joins to a further bracket 169 which is secured to the storage tank 134 by a horizontal pivot axis 171 which extends perpendicularly relative to the axis 168. This enables the nozzle member of each nozzle assembly to be suitably tilted both longitudinally and sidewardly so as to be properly oriented relative to the adjacent filter plate.

It will be appreciated that numerous variations can be made in the design of the nozzle assembly 133, specifically as to the design of the control piston 157 and its positional and cooperative relationships with respect to the supply passage 142 and the storage chamber 135. One such variation is illustrated by FIG. 15 which is structurally and functionally similar to FIG. 13 except that the ports 144 for supplying pressurized air into the chamber 135 communicate directly with the rearward end of the chamber 143, and the control piston 157 has an extension portion 157a which is slidably supported in the rearward or upstream end of the chamber 143 to close off the ports 144 when the control piston is in the rearward or opened position during discharge of the storage chamber 135. This arrangement for the control piston 157 effectively positively isolates the storage chamber 135 from the passage 142 during the discharge phase, and additionally increases the response time of the control piston 157 in returning to its closed position since all of the pressurized air upon being resupplied to the passage 142 initially reacts solely against the rearward end of the control piston to at least initiate movement thereof toward the closed position, prior to permitting the supply air to be fed into the storage chamber 135.

This embodiment of the filter press also preferably includes plate positioning assemblies 175 disposed inside of but on opposite sides of the arch-shaped shifter housing for controlling the positioning of the filter plate which is being moved from the closed stack into an opened position when discharge of filter cake is desired. The plate positioning assemblies 175 as disposed on opposite sides of the shifter housing, in the vicinity of but spaced upwardly from the opposite press side rails 14, are identical and only one such assembly 175 will be described in detail.

Referencing specifically FIGS. 11 and 12, this positioning assembly 175 is disposed adjacent the end of the arch-shaped shifter housing 22' which is opposite the shift units 41' and includes a small but vertically extending lower stop plate 176 which is fixedly secured to an upwardly projecting support 177. This latter support 177 is of a generally Z-shaped configuration and includes a lower part which is vertically slidably supported on the housing 22' by suitable guides 178, with the upper part of support 177 being vertically slidably supported on the housing 22' by further guides 179. The upper and lower portions of the support 179 are joined by an intermediate horizontally extending bight 181 to which is secured a downwardly projecting upper stop plate 180. The bight 181 mounts thereon an upwardly projecting bracket which joins to a clevis 182 provided on the lower end of a piston rod 183 which slidably projects downwardly from a conventional pressure cylinder 184 (such as an air cylinder), the housing of which is secured to the shifter housing 22'.

The bight part 181 also mounts thereon a vertically swingable latch member 185 which is hinged at 186 so that the latch member projects generally horizontally in the upstream direction toward the stack of closed plates. The free end of the latch member defines a cam surface 187 on the underside thereof which tapers downwardly in the opening direction of the plates, and terminates in a rearwardly oriented shoulder 188.

When the plate positioning arrangements 175 are in a lowered position due to downward extension of the air cylinders 184, the lower stop plates 176 are positioned lowermost so as to be positioned for abutment with the handles 28' of the filter plate 17'-1 when the latter is shifted into the opened position and is spaced a predetermined distance from the opposed leading or endmost plate 17'-2 associated with the closed stack. When in this opened position, wherein the handles of plate 17'-1 abut the stop plates 176, this plate 17'-1 may still be spaced a slight distance from the endmost plate 17'-3 of the stack of opened and cleaned plates as disposed adjacent the movable head 15'. The upper stop plate 180 is positioned directly behind the upper corner of the opened plate 17'-1, specifically directly behind the top tabs 69' which project from the upper corners of the plate, whereby the filter plate 17'-1 effectively abuts against the top stops 180 and the lower stops 176. At the same time, as the plate is moved toward the stop plates, the upper edge of the filter plate engages the cam surface 187 and causes the latch member 185 to pivot upwardly until the filter plate moves past the cam surface and substantially abuts the stop plates, whereupon the weight of the latch causes it to swing downwardly so that the shoulder 188 effectively overlies and abuts against the front face of the filter plate adjacent the upper end thereof, whereupon the upper edge of the filter plate is effectively captivated between the upper stops 180 and the shoulders 188. This results in the opened plate 17'-1 being securely and stationarily positioned prior to initiation of the air blasting operation, and at the same time ensures that this plate is positioned a predetermined distance from the opposed plate 17'-2. This maintaining of a predetermined spacing between the two opposed plates 17'-1 and 17'-2 can become significant in presses employing a large number of plates since, in such instance, it has been observed that the length of the closed stack of plates when in the closed filtration stage can be several inches less than the stack of plates positioned adjacent the moving head after emptying of the press. Thus, if the opened plate is always moved over into engagement with the stack of empty plates, the opening distance can progressively decrease throughout a cycle by as much as several inches from beginning to end, and such decrease can effect proper positioning of the nozzle assemblies relative to the filter plates.

The operation of the filter press according to the embodiment of FIGS. 11-14 is substantially the same as the operation described above. The portions of the operation which are different, specifically the portions of the operation as effected by the air-assist discharge mechanism 62' and the stop arrangements 175, however, will be briefly described.

When the filter press is to be emptied, the leading plate in the closed stack will be shifted into an opened position by the shifter assembly 41' in the same manner as described above relative to FIGS. 1-8. That is, the shifter cylinders are energized to cause the shifter plate 47' to engage the handles 18' of the endmost plate and then slidably shift this plate along the rails 14' into an opened position substantially as depicted by the plate 17'-1 in FIG. 11. In this embodiment, however, the air cylinders 184 of the plate positioning arrangement 175 have been previously energized downwardly to lower the stop plate 176 and 180, and the filter plate 17'-1 is shifted into an opened position until the plate substantially abuts the stop plates 176 and 180, at which time the latch members 185 also swing downwardly and engage the upper edge of the opened plate. As the shift cylinders extend so as to move the frontmost plate 17'-1 into the opened position, as this plate closely approaches the opened position, the shifter plate 47' contacts a limit switch which is mounted on the shifter housing in close proximity to the open position, causing activation of this limit switch. This transmits a signal to the controller 93 which turn transmits a signal terminating the forward extension of the shift cylinders. At that time a further signal is transmitted from the controller to the air discharge assembly 62' so as to initiate the operation thereof. The air cylinder 104' associated with the scissor mechanism 109' is energized to cause the scissor mechanism to extend downwardly and move the head assembly 80' downwardly between the opposed filter plates. Upon reaching the lower position, the cylinder 104' is reversely energized to retract the head assembly 80' back up into its uppermost position, thereby completely the cleaning cycle.

During the cyclic actuation of the head assembly 80', the nozzle assemblies 133 are preferably discharged several times at short timed intervals, preferably but optionally on both the downstroke and upstroke of the head assembly 80'. For example, each row of nozzle assemblies 133 will normally be first discharged just prior to or shortly after the initiation of downward vertical movement of the head assembly 80' so that high velocity air blasts are directed against the upper edges of the filter plates to assist in peeling the upper edge of the cake away from the underlying membrane or diaphragm. As the nozzle assemblies 133 are moved downwardly, the storage tanks 134 rapidly recharge, and the nozzle assemblies 133 are repeatedly discharged preferably at least three or four times as the head assembly 80' moves downwardly, with the last discharge being substantially at or adjacent the lowermost position of the head assembly so that an air blast can be directed against the lower portion of the filter plate diaphragms. It has been experimentally observed that the air discharges can occur at short time intervals, such as at about two second intervals, as the head assembly moves downwardly, and again similarly on the upstroke if desired.

The control for the sequential blasting of high velocity air pulses from the nozzle assemblies 133 originate from the controller 93 which can be suitably programmed to provide desired timing between adjacent discharges, and which provide timed activation of the control valves 164 so as to permit discharging of the supply passages 142 for a short duration, such as in the order of about 100 milliseconds, which is sufficient to allow each control piston 157 to shift into an open position and permit discharge of the respective charge of high pressure air stored in the respective storage chamber 135.

In addition, by providing each pair or grouping of nozzle assemblies 133 with its own respective control valve 164, then these control valves 164 can also be provided with control signals from the controller 93' at slightly different or delayed times so as to cause the various nozzle assemblies 133 within each row to be discharged in a slightly delayed and sequential manner relative to one another. This slightly delayed and sequential discharge of the nozzles within the row not only tends to reduce noise generated by the overall arrangement, but is also believed to provide additional turbulence and agitation transversely across the filter plate so as to possibly assist in dislodging the sticky cake from the membrane.

After the head assembly 80' completes the air discharge assist operation and returns to its raised position, then this transmit a signal to the controller 93' which in turn then transmit a signal to the shift cylinders so that the shift plates 47' are slightly retracted back into an intermediate position substantially as illustrated by the dotted line position in FIG. 11, and then transmits a signal to cylinders 184 which cause them to raise upwardly and lift the stop plates 176 and 180, and subsequentially a signal is transmitted to the shifter mechanism 41' to reinitiate the forward extension of the shift cylinders so that the shift plates 47' again engage the front filter plate 17'-1 and then shift it forwardly into engagement with the endmost plate 17'-3 of the open stack. The shifter mechanism then returns to its initial position, at reach position the shifter housing is shifted rearwardly until a proximity switch senses the presence of the handle on the next plate and stops the movement. The entire shifter housing and related mechanisms are now in position to permit initiation of a further cycle in the same manner as described above.

The filter press of the present invention, when incorporating the features of the second embodiment as illustrated by FIGS. 11-14, will also preferably but optionally include the bumping or vibrating devices 61 as previously described.

In addition, when using the air discharge assist mechanism 62', particularly on presses which employ relatively small filter plates, it is anticipated that the vertical traverse of the nozzles downwardly and upwardly along the filter plates may be eliminated, and instead the nozzles can be stationarily positioned adjacent the upper edge of the opened plates and utilized to discharge at least one, and preferably two or three, high velocity short duration air blasts downwardly against the upper edges of the filter cake to assist in discharging the cake from the plates.

In an exemplary embodiment of a filter press employing the air-assist discharge mechanism 62', the nozzle assemblies 133 will each have a separate storage chamber 135 having an air capacity which is preferably in the range of from about 0.1 to about 0.3 cubic feet, the charge of air which accumulates within the storage chamber 135 will have a maximum pressure which is preferably in the range of from about 80 to 120 psi, the control valve 164 for the respective nozzle assemblies will be opened for a time interval which will preferably be no greater than about 150 milliseconds, and typically in the range of from about 50 to 150 milliseconds to permit rapid and complete discharge of the pressurized air charge from the storage tank through the respective Laval nozzles, and the nozzle assemblies will be repeatedly discharged during each cake release cycle at short intervals in the range of from about one to about three seconds and preferably at about two second intervals.

While the invention as described above utilizes a separate air storage tank 134 for each nozzle 148, it will be appreciated that a single air storage tank may be provided for a grouping of nozzles, with the tank storage capacity being appropriately sized in accordance with the member of nozzles which are supplied with air therefrom. Such tank or tanks, however, are preferably mounted on the head assembly so as to be disposed in close proximity to the nozzles 148. Each such nozzle 148 should still preferably have its own control piston 157 associated therewith.

Additionally, while the invention as described above utilizes the plate positioning assemblies 175 for stopping the shifted plate at a predetermined distance from the remaining stack of plates, it will be appreciated that in some presses such plate positioning assemblies 175 can be eliminated and the shifted plate positioned directly adjacent the previously shifted plates prior to initiation of the air discharge cycle. In situations where the dimensional variation between the closed plate stack dimension and the opened plate stack dimension is insignificant, then the plate positioning assemblies 175 can be eliminated.

Further, while the press as described above utilizes support rollers disposed in engagement with elongate support rods, with one of the rollers being a frictional drive roller, such as the roller 32 and its driving engagement with the rod 25, nevertheless other types of drive devices can be provided. For example, the drive can comprise a gear-rack arrangement wherein the gear is mounted on the shifter and replaces the drive roller 32, and is disposed in rolling engagement with an elongate rack which is fixed to and extends horizontally of the press along one of the side rails 14.

Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

Claims

1. In a filter press including a frame having a pair of horizontally elongate and generally parallel side rails which extend lengthwise of the press and are sidewardly spaced apart, a first head structure stationarily mounted adjacent one end of said rails, a second head structure mounted on said rails for movement toward and away from said first head structure for respective closing and opening of said press, a plurality of vertically-enlarged filter plates movably disposed in generally side-by-side relationship to define a stack extending lengthwise between said first and second head structures when said press is closed, each said filter plate mounting thereon a respective filter member which is independent of the filter members mounted on the other filter plates, said filter plates extending transversely between and being slidably supported on said side rails, each movable filter plate having parts which project outwardly from opposite side edges thereof, and a shift assembly for effecting shifting of individual said filter plates along the side rails toward the second head structure when said second head structure is in an open position, the improvement comprising:

discharge assist means for directing a pressurized stream of air against an exposed face of an endmost said plate of said stack to assist in dislodging filtrate adhered to said plate, said discharge assist means including an air nozzle assembly for directing a pressurized airstream at the exposed face of said plate, and a drive device for moving the nozzle generally parallel across the face to effect air-assisted discharge throughout the entirety of the face.

2. A filter press according to claim 1, wherein said discharge assist mechanism includes means for causing the pressurized streams of air to be generated as a series of spaced but short duration air blasts having a velocity generally near sonic velocity.

3. A filter press according to claim 1, wherein said air nozzle assembly includes a plurality of nozzle means for discharging short duration blasts of air against the exposed face of the filter plate.

4. A filter press according to claim 3, wherein the nozzle means defining a Level-type nozzle for discharging air at a velocity generally near sonic velocity.

5. A filter press according to claim 3, wherein each said nozzle means includes a discharge nozzle disposed adjacent and oriented toward the exposed face of the filter plate and a separate air storage tank disposed adjacent and in fluid communication with the respective discharge nozzle, said storage tank defining therein a closed low-volume storage chamber for containing therein a quantity of highly pressurized air, said discharge nozzle including a converging-diverging configuration for discharging the air at a velocity which at least approaches sonic velocity, and shiftable control means for normally isolating the pressurized air in the storage chamber from the discharge nozzle and permitting the quantity of pressurized air in the storage tank to be blasted through the discharge nozzle when the shiftable control means is moved into an open position.

6. A filter press according to claim 5, including means for supplying pressurized air into the storage chamber when the shiftable control means is in a closed position, and said nozzle means including means for isolating said storage chamber from said supplying means when the shiftable control means is in said open position.

7. A filter press according to claim 6, including controller means for effecting sequential discharge of said nozzle means at timed intervals of short duration.

8. A filter press according to claim 7, wherein said shiftable control means includes a pressure-moved control member having a first pressure face acted on by the pressurized air supplied by said supplying means for normally maintaining the control member in the closed position, said control member having a second pressure face which is acted on by the pressurized air in said storage chamber, said second pressure face being opposed to and of smaller area than said first pressure face to cause the control member to be shifted into the opened position when the supply pressure against said first face is relieved.

9. A filter press according to claim 1, wherein the shifter assembly includes a plate shifter mechanism for effecting slidable shifting of an endmost plate from the stack along the support rails away from the stack toward the open second head structure into an opened position spaced a predetermined distance from a remaining endmost plate of the stack to define a gap therebetween;

said shift assembly including a shifter housing which is movably supported on said frame for movement lengthwise thereof, said shifter housing mounting said plate shifter mechanism thereon;

said discharge assist means being mounted on said shifter housing adjacent a side of said gap, and said discharge assist means including first and second said air nozzle assemblies which are respectively positioned for directing airstreams against exposed faces of the plates defining opposite ends of the gap; and

plate positioning means mounted on said shifter housing and including plate-contacting stop means movable from an inactive position spaced from the path of movement of the filter plates to an active position wherein the stop means are disposed for contacting the filter plate which is disposed in said opened position to prevent the plate from moving past the opened position.

10. A filter press according to claim 9, including a motive means controlled by said controller means for moving said stop means into said inactive position after the airstreams have been discharged against the plates and for initiating forward movement of said shifter mechanism to move said opened plate forwardly from said opened position toward the open second head structure.

11. A process for discharging filtrate from filter plates of a filter press, comprising the steps of:

providing an elongated stack of upright filter plates positioned in adjacent, side-by-side contacting relationship;

moving an endmost plate of said stack a predetermined distance away from the stack to define a gap between said endmost plate and a next adjacent plate of said stack;

providing a discharge assist means for discharging a series of short-duration air blasts at a velocity which at least approaches sonic velocity;

simultaneously discharging said series of short-duration high-velocity air blasts against the opposed exposed faces of said endmost and next adjacent plates to assist in removing filtrate adhered to said opposed exposed faces; and

sequentially repeating the above steps.

12. A process according to claim 11, including the steps of:

providing a plurality of nozzles laterally adjacent one side of said gap on said discharge assist means;

moving said plurality of nozzles into said gap so that the nozzles are moved in spaced but generally parallel relationship across the opposed exposed faces; and

directing said air blasts from said nozzles against the opposed exposed faces as the nozzles are moved therealong.

13. A process according to claim 12, wherein the series of short-duration high-velocity air blasts are discharged from said nozzles in spaced times intervals as the nozzles are moved cross the opposed exposed faces.

14. A process according to claim 13, including the step of transversely bumping solely the next adjacent plate to at least partially loosen filtrate adhered to said plate prior to moving said next adjacent plate away from the stack.

15. A process according to claim 12, including the step of transversely bumping solely the next adjacent plate to at least partially loosen filtrate adhered to said plate prior to moving said next adjacent plate away from the stack.